Transport Processes in a Eukaryotic Cell
Properties of the two types of transport: Passive and Active
Channel and Carrier Proteins
Channel proteins are only responsible for passive transport, while carrier proteins are responsible for both passive and active transport
Channel proteins are only responsible for passive transport, while carrier proteins are responsible for both passive and active transport
Carrier proteins bind one or more solute molecules on one side of the membrane, undergo a conformation change, and then deposit the solute molecules on the other side of the membrane
The glucose transporter, GLUT1, found in erythrocytes (a blood cell), is shown in its two conformations moving a glucose from the blood into the cell (the glucose is quickly phosphorylated within the cell so it cannot leave the cell)
Channel proteins tend to be ion channels and include three types which have both open and closed conformations (these channels are referred to as gated channels)The Na+-K+ ATPase:
Required to maintain K+ high inside the cell and Na+ high outside the cell which is important to maintain the electrochemical gradient
Required to maintain K+ high inside the cell and Na+ high outside the cell which is important to maintain the electrochemical gradient
The Na/K pump is usually made up of two alpha and two beta subunits. The alpha subunits are transmembrane proteins that have ATP binding sites on the cytoplasmic side. The beta subunits are located on the outer side of the membrane and are glycosylated. This figure shows the protein in the E1 conformation, meaning it is open to the cytosol. When Na+ ions bind, the protein changes to the E2 conformation, which opens to the outside. As shown in the figure, the pump is inhibited by oubain.
No comments:
Post a Comment